Ether composition

ABSTRACT

An ether composition and a lubricant which bond to substrates with a high bonding ratio and form a coating having a low friction coefficient surface are provided. 
     An ether composition comprising at least two compounds selected from (X—) 3 Y 3 , (X—) 2 Y 3 —Z and X—Y 3 (—Z) 2  wherein the total number of moles of CF 3  groups in Z in relation to the sum of the total number of moles of CF 3  groups in Z and the total number of moles of OH groups in X is at least 0.001 and at most 0.30. X is HO—(CH 2 CH 2 O) a .(CH 2 CH(OH)CH 2 O) b -Q-, Y 3  is a perfluoroalkane-triyl group, and Z is CF 3 (CF 2 ) s O(CF 2 CF 2 O) g —, wherein a is an integer of from 0 to 100, b is 0 or 1, s is an integer of from 0 to 19, g is an integer of from 3 to 200, and Q is a polyfluorinated polymethylene group or a polyfluorinated polymethylene group having an etheric oxygen atom bonded between carbon-carbon atoms and/or an etheric oxygen atom bonded to the terminal carbon atom bonded to Y 3 .

TECHNICAL FIELD

The present invention relates to an ether composition useful as alubricant, etc.

BACKGROUND ART

A perfluorinated polyether compound (hereinafter referred to as PFPE) isused as a lubricant, etc. to be applied to the surface of a magneticrecording medium (Non-Patent Document 1).

As such a lubricant, PFPE having two CH₂OH groups at its molecularterminals has been commonly used.

Further, the present applicant has proposed the following as PFPE or itscomposition, which is useful as a lubricant, etc.

(1) PFPE having three CH₂OH groups, or PFPE having two CH₂OH groups andone CF₃ group (Patent Document 1).

(2) An ether composition comprising two types of PFPEs different in themolecular weight (Patent Document 2).

In recent years, along with an increase in the recording density of amagnetic recording medium, narrowing of a space between a recordingelement and a magnetic recording medium and a trend for high speed ofrotation of a magnetic recording medium have been advanced. Accordingly,the application environment of a lubricant to be applied on the surfaceof a magnetic recording medium has been increasingly severe. Therefore,the lubricant is required to have the following properties.

(i) It has a high fixative to a magnetic recording medium, along withthe trend for high speed of the magnetic recording medium.

(ii) It forms a coating having a low friction coefficient surface sothat when a recording head contacts magnetic recording media, the impactby the contact is dissipated.

However, PFPE heretofore proposed did not provide sufficient performanceto meet such requirements.

-   Non-Patent Document 1: “Monthly TRIBOLOGY”, 1995, vol. 99, November    issue, p. 37-38-   Patent Document 1: WO2005/068534-   Patent Document 2: WO2007/013412

DISCLOSURE OF THE INVENTION Object to be Accomplished by the Invention

The object of the present invention is to provide an ether compositionwhich bonds to substrates with a high bonding ratio and forms a coatinghaving a low friction coefficient surface and a lubricant containing theether composition.

Means to Accomplish the Object

The ether composition of the present invention is an ether compositioncomprising at least two compounds selected from the group consisting ofa compound represented by the following formula (A1), a compoundrepresented by the following formula (A2) and a compound represented bythe following formula (A3), wherein the total number of moles of CF₃groups in the group represented by the following formula (Z) in relationto the sum of the total number of moles of CF₃ groups in the grouprepresented by the following formula (Z) and the total number of molesof OH groups in the group represented by the following formula (X)(CF₃/(OH+CF₃)) is at least 0.001 and at most 0.30:

(X—)₃Y³  (A1),

(X—)₂Y³—Z  (A2),

X—Y³(—Z)₂  (A3).

Wherein X is a group represented by the following formula (X),

Y³ is a perfluoroalkane-triyl group or a perfluoroalkane-triyl grouphaving an etheric oxygen atom inserted between carbon-carbon atoms,provided that when Y³ has a CF₃ group, the CF₃ group is bonded to aquaternary carbon,

Z is a group represented by the following formula (Z):

HO—(CH₂CH₂O)_(a).(CH₂CH(OH)CH₂O)_(b)-Q-  (X),

CF₃(CF₂)_(s)O(CF₂CF₂O)_(g)—  (Z).

Wherein in the above formulae (X) and (Z), a is an integer of from 0 to100, b is 0 or 1, s is an integer of from 0 to 19, g is an integer offrom 3 to 200, and Q is a polyfluorinated polymethylene group, apolyfluorinated polymethylene group having an etheric oxygen atom bondedbetween carbon-carbon atoms, a polyfluorinated polymethylene grouphaving an etheric oxygen atom bonded to the terminal carbon atom bondedto Y³ or a polyfluorinated polymethylene group having an etheric oxygenatom bonded between carbon-carbon atoms and an etheric oxygen atombonded to the terminal carbon atom bonded to Y³.

It is preferred that the group (X) is a group selected from the groupconsisting of a group represented by the following formula (X1), a grouprepresented by the following formula (X2), a group represented by thefollowing formula (X3) and a group represented by the following formula(X4):

HOCH₂CF₂O(CF₂CF₂O)_(d)—  (X1),

HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂CF₂O)_(d)—  (X2),

HOCH₂CH₂CF₂O(CF₂CF₂O)_(d)—  (X3),

HOCH₂CH₂OCH₂CF₂O(CF₂CF₂O)_(d)—  (X4),

wherein d is an integer of from 1 to 200.

It is preferred that Y³ is a group selected from the group consisting ofa group represented by the following formula (Y³-1), a group representedby the following formula (Y³-2) and a group represented by the followingformula (Y³-3).

It is preferred that the compound represented by the formula (A1) is acompound represented by the following formula (A1-1), that the compoundrepresented by the formula (A2) is a compound represented by thefollowing formula (A2-1a), a compound represented by the followingformula (A2-1b) or a combination of a compound represented by thefollowing formula (A2-1a) and a compound represented by the followingformula (A2-1b), and that the compound represented by the formula (A3)is a compound represented by the following formula (A3-1a), a compoundrepresented by the following formula (A3-1b) or a combination of acompound represented by the following formula (A3-1a) and a compoundrepresented by the following formula (A3-1b).

It is preferred that the compound represented by the formula (A1), thecompound represented by the formula (A2) and the compound represented bythe formula (A3) have no —OCF₂O— structure.

It is preferred that the he total amount of the compound represented bythe formula (A1), the compound represented by the formula (A2) and thecompound represented by the formula (A3) is at least 95 mass % inrelation to the ether composition.

It is preferred that the ether composition has a number averagemolecular weight of from 500 to 1,000,000 and a molecular weightdistribution (mass average molecular weight/number average molecularweight) of from 1.01 to 1.5.

The ether composition is preferably used to form a lubricant containingthe ether composition.

EFFECTS OF THE INVENTION

The ether composition of the present invention bonds firmly tosubstrates, forms a coating having a surface with a low coefficient offriction and is useful as a lubricant to be applied on the surface ofmagnetic recording media.

BEST MODE FOR CARRYING OUT THE INVENTION

In this specification, a compound represented by the formula (A1) isreferred to as the compound (A1). Compounds represented by the otherformulae are referred to in the same manner.

Further, a group represented by the formula (X) is referred to as thegroup (X). Groups represented by the other formulae are referred to inthe same manner.

The ether composition of the present invention is an ether compositioncomprising at least two compounds selected from the compound (A1), thecompound (A2) and the compound (A3), and preferably comprises thecompound (A1) and the compound (A2), or the compounds (A1) to (A3). Eachof the compounds (A1) to (A3) in the ether composition may consist ofone or at least two compounds and preferably consists of one compound.

(X—)₃Y³  (A1),

(X—)₂Y³—Z  (A2),

X—Y³(—Z)₂  (A3).

X is a group (X).

HO—(CH₂CH₂O)_(a).(CH₂CH(OH)CH₂O)_(b)-Q-  (X).

The notation of the structure —(CH₂CH₂O)_(a).(CH₂CH(OH)CH₂O)_(b)— meansthat when at least one unit is present with respect to each of the(CH₂CH₂O) unit and the (CH₂CH(OH)CH₂O) unit, their arrangement is notparticularly limited. Namely, in a case where one unit is present withrespect to both units, the unit which is bonded to the terminal hydroxylgroup may be either of them. Further, the structure—(CH₂CH₂O)_(a).(CH₂CH(OH)CH₂O)_(b)— may be a block copolymer or a randomcopolymer.

Q is a polyfluorinated polymethylene group, a polyfluorinatedpolymethylene group having an etheric oxygen atom bonded betweencarbon-carbon atoms, a polyfluorinated polymethylene group having anetheric oxygen atom bonded to the terminal carbon atom bonded to Y³ or apolyfluorinated polymethylene group having an etheric oxygen atom bondedbetween carbon-carbon atoms and an etheric oxygen atom bonded to theterminal carbon atom bonded to Y³. The polyfluorinated polymethylenegroup means a group having at least two hydrogen atoms in —(CH₂)_(t)—(wherein t is an integer of at least 2) substituted by fluorine atoms. Qis preferably a group represented by the formula—(CH₂)_(c)—CF₂O(CF₂CF₂O)_(d)— (wherein the right hand side terminal ofthe group is bonded to Y³, c is an integer of from 1 to 100, and d is aninteger of from 1 to 200).

a is an integer of from 0 to 100, preferably an integer of from 0 to 10,more preferably an integer of from 0 to 2, particularly preferably 0or 1. When b is 1, a is preferably 0.

b is preferably 0 or 1.

The group (X) is preferably a group (X′).

HO—(CH₂CH₂O)_(a).(CH₂CH(OH)CH₂O)_(b)—(CH₂)_(c)—CF₂O(CF₂CF₂O)_(d)—  (X′),

wherein a to d are the same as defined above.

c is preferably an integer of from 1 to 10, more preferably 1 or 2.

d is preferably an integer of from 3 to 100, more preferably from aninteger of from 5 to 50.

When two or more groups (X) are present in one molecule, they may be thesame or different. Groups (X) having different numbers of structuralunits may be categorized as the same. For example, the same groups mayhave the same d or may be different only in d. With respect to thenumbers other than d, groups (X′) which are different in a, b or c areconsidered as different groups. When two or more groups (X) are in thesame molecule, it is preferred that they are the same groups.

The group (X) is preferably a group (X1), a group (X2), a group (X3) ora group (X4), and a group (X1) or a group (X2) is more preferred in viewof easy production and stability of the compounds (A1) to (A3).

HOCH₂CF₂O(CF₂CF₂O)_(d)—  (X1),

HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂CF₂O)_(d)—  (X2),

HOCH₂CH₂CF₂O(CF₂CF₂O)_(d)—  (X3),

HOCH₂CH₂OCH₂CF₂O(CF₂CF₂O)_(d)—  (X4).

Y³ is a perfluoroalkane-triyl group or a perfluoroalkane-triyl grouphaving an etheric oxygen atom inserted between carbon-carbon atoms, andwhen Y³ has a CF₃ group, the CF₃ group is bonded only to a quaternarycarbon.

A perfluoroalkane-triyl group means a trivalent saturated hydrocarbongroup having all hydrogen atoms substituted by fluorine atoms, and aquaternary carbon atom which is not bonded to a fluorine atom may bebonded to a CF₃ group.

Y³ is restricted to a group having no CF₃ groups or having only a CF₃group bonded to a quaternary carbon atom for the following reason.

The present inventors studied the effect of the structure of PFPEs ontheir low friction coefficient and firm bonding, which are incompatiblewith each other, and found that a CF₃ group bonded to a secondary carbonatom (CF₂) or a tertiary carbon atom (CF) has a high degree of freedomin the molecule and hence contributes to decrease in frictioncoefficient (decrease in viscosity), while inhibiting firm bonding.Therefore, the present inventors decided that the proportion of CF₃groups in an ether composition should be controlled to attain both a lowfriction coefficient and firm bonding and that PFPE should have a CF₃group which is present only at the terminal of Z and may have anotherCF₃ group attached to a quaternary carbon atom with a relatively lowdegree of freedom in Y³.

Y³ may be a group having an etheric oxygen atom inserted betweencarbon-carbon atoms. The number of etheric oxygen atoms, if present, ispreferably 1 to 3. Because an etheric oxygen atom is present betweencarbon-carbon atoms, no etheric oxygen atom can be present at theterminal of Y³ bonded to X or Z. When Y³ contains an etheric oxygenatom, it is preferred that Y³ contains no —OCF₂O— structure and has no—OCF₂— structure at the terminal bonded to X or Z. Compounds havingneither structure have a remarkably improved chemical stability.

Y³ is preferably a group having no etheric oxygen atom, particularlypreferably a group (Y³-1), a group (Y³-2) or a group (Y³-3).

Z is a group (Z).

CF₃(CF₂)_(s)O(CF₂CF₂O)_(g)—  (Z).

s is an integer of from 0 to 19, preferably an integer of from 0 to 15,particularly preferably an integer of from 0 to 5.

g is an integer of from 3 to 200, preferably an integer of from 3 to100, more preferably an integer of from 3 to 70, particularly preferablyan integer of from 5 to 50.

Groups (Z) in which s is the same are considered to be the same,irrespective of whether g is the same or different. The groups (Z) arepreferably the same.

The group (Z) contributes to decrease in friction coefficient and ispreferred to have a certain length in view of increasing the freedom ofthe CF₃ group in the molecule. The group (Z) is preferably a group (Z1),a group (Z2) or a group (Z3).

CF₃O(CF₂CF₂O)_(g)—  (Z1),

CF₃(CF₂)₂O(CF₂CF₂O)_(g)—  (Z2),

CF₃(CF₂)₅O(CF₂CF₂O)_(g)—  (Z3).

Each of the compounds (A1) to (A3) may be a combination of two or morecompounds which preferably have the same Y³ but differ in a, b, c or din the group (X). In the group (X), the average of a is preferably apositive number of from 0 to 2, particularly preferably 0. In the group(X′), the average of c is preferably 1, and the average of d ispreferably a positive number of from 3 to 100. In the group (Z), theaverage of g is preferably a positive number of from 3 to 100.

It is preferred that the compounds (A1) to (A3) have no —OCF₂O—structure in view of chemical stability. A compound having no —OCF₂O—structure means a compound in which the presence of the structure cannotbe detected by a conventional analytical means (such as ¹⁹F-NMR).

As the compound (A1), a compound (A11) or a compound (A12) is preferred.

{HOCH₂CF₂O(CF₂CF₂O)_(d)—}₃Y³  (A11),

{HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂CF₂O)_(d)—}₃Y³  (A12).

As the compound (A2), a compound (A21) or a compound (A22) is preferred.

{HOCH₂CF₂O(CF₂CF₂O)_(d)—}₂Y³—(OCF₂CF₂)_(g)O(CF₂)_(S)CF₃  (A21),

{HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂CF₂O)_(d)—}₂Y³—(OCF₂CF₂)_(g)O(CF₂)_(s)CF₃  (A22).

As the compound (A3), a compound (A31) or a compound (A32) is preferred.

HOCH₂CF₂O(CF₂CF₂O)_(d)—Y³{—(OCF₂CF₂)_(g)O(CF₂)_(s)CF₃}₂  (A31),

HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂CF₂O)_(d)—Y³{—(OCF₂CF₂)_(g)O(CF₂)_(s)CF₃}₂  (A32).

When Y³ is the group (Y³-1), the compound (A1) is preferably a compound(A1-1), the compound (A2) is preferably a compound represented by thefollowing formula (A2-1a), a compound represented by the followingformula (A2-1b) or a combination of a compound represented by thefollowing formula (A2-1a) and a compound represented by the followingformula (A2-1b), and the compound (A3) is preferably a compoundrepresented by the following formula (A3-1a), a compound represented bythe following formula (A3-1b) or a combination of a compound representedby the following formula (A3-1a) and a compound represented by thefollowing formula (A3-1b).

The present inventors found that the friction coefficient and thebonding ratio vary depending on the proportion of groups (Z) andtherefore decided that the ratio of groups (Z) is within a specificrange. Namely, the total number of moles of CF₃ groups in the group (Z)in relation to the sum of the total number of moles of CF₃ groups in thegroup (Z) and the total number of moles of OH groups in the group (X)(CF₃/(OH+CF₃), hereinafter referred to as CF₃ ratio) is at least 0.001and at most 0.30. CF₃ ratio is preferably at least 0.01 and at most0.30. By virtue of the CF₃ ratio within a specific range, the ethercomposition of the present invention can attain a low frictioncoefficient and a high bonding ratio. When the CF₃ ratio in thecomposition is too high, the effect of lowering the friction coefficientis not expected, and trouble such bleed out is aggravated. When the CF₃ratio is too low, the friction coefficient becomes large. However, thecomposition of the present invention having a low CF₃ ratio and morethan two compounds has such an effect that it is unlikely to adhere toother substances in contact with it.

The CF₃ ratio can be determined by identifying the structures of thecompounds in the ether composition and then measuring their contents, ordirectly from the ether composition.

Specifically speaking, when NMR is used for the determination, the ethercomposition is analyzed by ¹⁹F-NMR, and the peak area for CF₃ groups isdetermined. The chemical shift of —OCF₃ is observed around −54.0 to−56.0 ppm.

The number of terminal OH groups is determined from the area of the peakattributed to the fluorine atoms in CF₂ around −80 to −81.0 ppm in the¹⁹F-NMR spectrum when the terminal groups are —CF₂CH₂OH, from the areaof the peak attributed to the fluorine atoms in CF₂ around −75.0 to−78.0 ppm in the ¹⁹F-NMR spectrum when the terminal groups are—CF₂CH₂OCH₂CH(OH)CH₂OH, or from the area of the peak attributed to thefluorine atoms in CF₂ around −78.0 to −80.0 ppm in the ¹⁹F-NMR spectrumwhen the of terminal groups are —CF₂CH₂(OCH₂CH₂)_(g)OH.

The number of terminal OH groups can also be determined by measuring—OCF₃ by ¹⁹F-NMR and ¹H-NMR using a compound having both hydrogen andfluorine atoms such as bistrifluoromethylbenzene as an internal control.

For example, it is determined from the area of the peak attributed toCH₂ around 4.0 to 4.1 ppm in the ¹H-NMR spectrum when the terminalgroups are —CF₂CH₂OH, from the area of the peak attributed to CH₂ nextto CF₂ around 3.8 to 4.0 ppm or the area of the prak attributed to CH₂in terminal CH₂OH around 3.5 ppm when the terminal groups are—CF₂CH₂O(CH₂CH₂O)_(g)—H, or from the area of the peak attributed to CHin CH(OH) around 3.7 to 3.9 ppm.

In the case of a compound having both —CH₂CH(OH)CH₂— and —CH₂CH₂O—,because ¹H-NMR signals to be used for determination of the number of OHgroups overlap, the OH groups attached to these groups are converted toCF₃C(O)O— or CH₃C(O)O— groups etc., and the number of OH groups isdetermined from the area of the chemical shift peak of such a group inthe ¹H-NMR or ¹⁹F-NMR spectrum.

Further, in ¹H-NMR analysis, the peak attributed to OH groups can shiftand overlap with the zone important for identification around 3.5 to 3.8ppm, depending on the measurement environment (such as pH). Therefore,it is preferred to deutrate the hydrogen in OH groups by adding a traceamount of a deuterated solvent (such as heavy water) to a sample toshift the peak attributed to OH groups so that the peak does not overlapwith the previously mentioned peaks.

It is preferred that the ether composition of the present invention doesnot contain a compound (A4). By not containing the compound (A4), it ismeans that the compound (A4) is not contained at all, or even ifpresent, its content measured by high performance liquid chromatography(hereinafter referred to as HPLC) is at most 2.0 mass %.

Y³(—Z)₃  (A4).

By virtue of the absence of a compound (A4) in the ether composition ofthe present invention, it is possible to suppress bleed out and toprovide a lubricant which firmly bonds to a substrate. It is preferredto remove the compound (A4) from the ether composition by thepurification method mentioned later.

The total amount of the compounds (A1) to (A3) is preferably at least 95mass % in relation to the ether composition, more preferably at least 98mass %.

When the ether composition consists of a compound (A1) and a compound(A2), the mass ratios (mass %) of the compound (A1) and the compound(A2) in the ether composition is from 50 to 95 for the compound (A1) andfrom 5 to 50 for the compound (A2), preferably from 60 to 80 for thecompound (A1) and from 20 to 40 for the compound (A2).

Further, when the ether composition consists of the compounds (A1) to(A3), the ratios (mass %) of the compound (A1), the compound (A2) andthe compound (A3) in the ether composition are from 50 to 90 for thecompound (A1), from 5 to 50 for the compound (A2) and from 1 to 25 forthe compound (A3), preferably from 60 to 80 for the compound (A1), from10 to 20 for the compound (A2) and from 5 to 10 for the compound (A3).

The number average molecular weight (hereinafter referred to as Mn) ofthe ether composition is preferably from 500 to 1,000,000, morepreferably from 500 to 100,000, particularly preferably from 1,000 to20,000.

The molecular weight distribution (hereinafter referred to as Mw/Mn) ofthe ether composition is preferably from 1.01 to 1.5, more preferablyfrom 1.01 to 1.25. Herein, Mw is the mass average molecular weight.

When the Mn and the Mw/Mn are within the above ranges, the ethercomposition has a low viscosity, contains a small amount of evaporativecomponents and dissolves homogeneously in a solvent.

The Mn can be measured by gel permeation chromatography (hereinafterreferred to as GPC). The Mw/Mn is determined from the Mn and the Mwmeasured by GPC.

The ether composition of the present invention may be prepared by thefollowing methods.

Method 1: Prepare and purify the compounds (A1) to (A3) respectively andformulate them into a composition.

Method 2: Prepare the compounds (A1) to the compound (A3) so that theresulting reaction product also contains the other two as by-products,and purify the reaction product to a certain CF₃ ratio to obtain acomposition.

Method 3: Mix two or more compositions obtained after purification inthe method 2 into a single composition.

For example, in the method 1, the compound (A1) can be prepared inaccordance with the method disclosed in Patent Document 1, and thecompounds (A2) and (A3) can be prepared in accordance with the methoddisclosed in Patent Document 1 by carrying out the reaction by usingstarting materials for the compounds (A2) and the compound (A3) insteadof the starting material for the compound (A1).

In the method 2, a reaction product containing by-products can beobtained by carrying out a reaction in the same manner as in the method1 or under modified reaction conditions. For example, in a process forpreparing the compound (A1) comprising liquid phase fluorination, undersevere reaction conditions, the compounds (A2) to (A4) having terminalCF₃ groups can be formed by cleavage of molecular terminals. In liquidphase fluorination, the fluorine gas concentration in the gas blown intothe liquid phase is preferably from 5.0 to 50 vol %, more preferablyfrom 10 to 30 vol % in view of suppression of formation of the compound(A4).

Under certain reaction conditions, the product of the liquid phasefluorination may contain the compound (A4). If contained, the compound(A4) is preferred to be removed by purification.

As a means for the purification, removal of e.g. metal impurities andanion impurities by an ion adsorbing polymer, supercritical extractionand column chromatography may be mentioned, and it is preferred tocombine them.

The ether composition of the present invention may be used as it is,after addition of other compounds or as an additive for other compounds.

The ether composition of the present invention may be used as it is orin combination with other substances. For example, as a lubricantcontaining the ether composition of the present invention, thecomposition may be used as it is.

Further, PFPE other than the compounds (A1) to (A3) (hereinafterreferred to as other PFPE-XX) may be added to the ether composition.When a PFPE-XX is added to the ether composition of the presentinvention, its amount is preferably at most 10 mass %, more preferablyat most 5 mass % in relation to the total amount of the ethercomposition (the ether composition of the present invention and thePFPE-XX) so that the present invention can show its characteristicssufficiently.

Further, the ether composition of the present invention may be added toPFPE-XX. The content of the PFPE-XX is preferably at most 50 mass %,more preferably at most 30 mass %, in relation to the total amount ofthe ether composition. By adding the ether composition of the presentinvention to PFPE-XX, it is possible to adjust the viscosity of thePFPE-XX and improve the bonding of the PFPE-XX.

Examples of the PFPE-XX used in combination with the ether compositionof the present invention include PFPEs-XX having a terminal hydroxylgroup and PFPEs-XX having a UV-absorbing terminal group such as thosementioned below.

<PFPEs-XX having a terminal OH group>

FOMBLIN Z-DiOL, FOMBLIN Z-TetraOL, DEMNUM SA and the like.

<PFPEs-XX having a UV-absorbing terminal group>

FOMBLIN Z-DIAC, FOMBLIN Z-DEAL, FOMBLIN AM2001, FOMBLIN Z-DISOC, DEMNUMSH, MorescoA20H and the like.

As another example of PFPE-XX, an ether compound (A⁴) having from 1 to 4groups (X) and from 0 to 3 groups (Z) and having at least 4 groups (X)and (Z) in total may be mentioned.

The ether compound (A⁴) is preferably at least one member selected froma compound (A⁴1), a compound (A⁴2), a compound (A⁴3) and a compound(A⁴4).

(X—)₄Y⁴  (A⁴1),

(X—)₃Y⁴—Z  (A⁴2),

(X—)₂Y⁴(—Z)₂  (A⁴3),

X—Y⁴(—Z)₃  (A⁴4).

X is a group (X), Y4 is a perfluoroalkane-tetrayl group or aperfluoroalkane-triyl group having an etheric oxygen atom insertedbetween carbon-carbon atoms and having no structure of the group (Z),and Z is a group (Z).

The group (X) is preferably the group (X1), the group (X2), the group(X3) or the group (X4), and the group (X1) or the group (X2) is morepreferred in view of the ease of production of the compounds (A⁴1) to(A⁴4) and their stability.

Y⁴ is preferred to have no CF₃ group.

Y⁴ is preferably any one of the groups (Y⁴-1) to (Y⁴-4), and the group(Y⁴-1) is particularly preferred because these compounds are easy tosynthesize, are chemically stable and have low crystallinity.

When the ether composition of the present invention and a PFPE-XX areused in combination, the CF₃ ratio in the whole composition ispreferably adjusted to at least 0.001 and at most 0.30 in order for theether composition of the present invention to exert its performance. ThePFPE-XX is preferred not to contain a PFPE having only CF₃ groups at theterminals. In this case, the total number of moles of OH groups coversall the terminal OH groups, and the total number of moles of CF₃ groupscovers all the CF₃ groups other than those attached to a quaternarycarbon atom. These total numbers of moles can be determined by NMR aspreviously described.

Further, it is preferred to use a PFPE-XX having a number averagemolecular weight of from 1,000 to 10,000 as the PFPE-XX.

The ether composition of the present invention is preferably used as asolvent composition by dissolving or dispersing the ether composition ina solvent.

The solvent is preferably a perfluoroamine (such asperfluorotripropylamine or perfluorotributylamine), a perfluoroalkane(such as Vertrel XF (manufactured by DuPont)) or a hydrofluoroether(such as AE-3000 (manufactured by Asahi Glass Company, Limited)), and ahydrofluoroether is more preferred in view of its low ozone depletingpotential.

The solvent composition may be a solution, a suspension or an emulsionand is preferably a solution.

The concentration of the ether composition of the present invention inthe solvent composition is preferably from 0.001 to 50 mass %, morepreferably from 0.01 to 20 mass %.

The solvent composition may contain or may not contain an additionalcomponent other than the ether composition of the present invention andthe solvent (hereinafter referred to additional component). When thesolvent composition is used as a lubricant, the additional component maybe a radical scavenger (such as X1p (manufactured by Dow Chemicals)) orthe like.

When the solvent composition is used as a surface modifier, theadditional component may be a coupling agent (of a silane, epoxy,titanium or aluminum type). Such a coupling agent improves adhesionbetween a substrate and a coating.

It is preferred that the solvent composition does not contain metalions, anions, water, low molecular weight polar compounds or the likebecause otherwise, the solvent composition would not show the intendedperformance.

Ions of metals (such as Na, K, Ca and Al) can form Lewis acid catalystswith anions which catalyze decomposition of PFPEs. Anions (of F, Cl,NO₂, NO₃, PO₄, SO₄, C₂O₄ and the like) and water can corrode the surfaceof a substrate. Therefore, the water content of the solvent compositionis preferably at most 2,000 ppm. Low molecular weight polar compounds(such as alcohols, plasticizers eluted from resins) can impair theadhesion between a substrate and a coating.

When the ether composition of the present invention is used as alubricant for magnetic disks, it is used in the same manner asconventional lubricants. For example, it is applied to the surface of asubstrate for a magnetic disk by roll coating casting, dip coating(dipping), spin coating, water casting, die coating, Langmuir-Blodgettfilm formation or vacuum vapor deposition, and dip coating, spin coatingor vacuum vapor deposition is preferred.

The substrate may be a NiP-plated substrate (aluminum, glass or thelike) having a primer layer, a recording layer and a carbon protectivelayer in this order.

The carbon protective layer is preferably at most 5.0 mm thick andpreferably has an average surface roughness (Ra) of at most 2.0 mm.

After application of a lubricant, a magnetic disk having a lubricantlayer is preferably subjected to adsorption treatment so that thelubricant is adsorbed onto the surface of the carbon protective layer.

The adsorption treatment may be heat treatment, infrared treatment, UVtreatment or plasma treatment, and is preferably heat treatment or UVtreatment, more preferably heat treatment. Further, after adsorptiontreatment, the magnetic disk may be washed with a fluorine-containingsolvent for the purpose of removal of contaminants and an excess of thelubricant.

The surface of the lubricant coating after the adsorption treatment hasgood water repellency enough to keep the inside the magnetic disk offwater and shows good lubricity for a long time.

The bonding ratio of the ether composition of the present inventionafter adsorption treatment can be at least 60%. It is preferably atleast 65%, particularly preferably at least 70%.

The contact angle of water (at room temperature) on the surface of amagnetic disk treated with the ether composition of the presentinvention can be at least 80°. It is preferably at 85°.

The preferred thickness of a coating formed of the ether composition ofthe present invention is at most 5.0 nm, more preferably at most 3.0 nm,particularly preferably at most 2.0 nm, in view of improvement ofrecording density and durability.

The ether composition of the present invention can be applied tosurfaces other than those of magnetic disk substrates. For example, itis useful as a surface modifier to be applied to the surfaces of polymersubstrates for control of the refractive indices of the substrates, as asurface modifier for improvement in the chemical resistance of polymersubstrates by surface modification, as an additive to be added to a wirecoating material, an ink repellent (for example, for coating or for aprinter such as an ink jet printer), an adhesive for semiconductordevices (such as an adhesive for lead on chip tape, a protective coatingfor semiconductor (such as a moistureproof coating agent or an ascentinhibitor for soldering) or a thin membrane (such as a pelliclemembrane) to be used in optical field, a lubricant for an antireflectionfilm for displays and an antireflection film for resists.

A coating formed from the ether composition of the present invention istransparent, has a low refractive index, and is excellent in heatresistance and chemical resistance. Further, the coating has highlubricity and has self-replenishing property.

The ether composition of the present invention is also useful as asurfactant. For example, it may be used as an additive to lower thesurface tension of paint, a leveling agent for paint or a leveling agentfor a polishing liquid. When it is added to paint, it is preferablyadded in an amount of from 0.01 to 5 mass % in relation to the paint.

EXAMPLES

Now, the present invention will be described in further detail withreference to Examples. However, it should be understood that the presentinvention is by no means thereby restricted.

In the following:

tetramethylsilane is abbreviated as TMS,

CCl₂FCClF₂ is abbreviated as R-113,

dichloropentafluoropropane is abbreviated as R-225,

CClF₂CClFCF₂OCF₂CClF₂ is abbreviated as CFE-419,

hexafluoroisopropyl alcohol is abbreviated as HFIP, and

Isopropyl alcohol is abbreviated as IPA.

(NMR Analysis)

TMS was used as a standard substance for ¹H-NMR (300.4 MHz), and CFCl₃was used as a standard substance for ¹⁹F-NMR (282.7 MHz). R-113 was usedas a solvent for NMR, unless otherwise specified.

(HPLC Analysis)

The ratios of the compounds in the composition were determined with aHPLC analyzer (Prominence, manufactured by Shimadzu Corporation) underthe following conditions. Specifically, in each run, the HPFIPconcentration in the mobile phase was gradually increased from 0% to100%, and the mass ratios of compounds in the composition eluted indescending order of the number of OH groups were determined.

Analytical column: normal phase silica gel column (SIL-gel, manufacturedby YMC Co., Ltd.)

Mobile phase: R-225 (ASAHIKLIN AK-225G, manufactured by Asahi GlassCompany, Limited) and HFIP

Mobile phase flow rate: 1.0 mL/min

Column temperature: 37° C.

Detector: evaporative light scattering detector

(GPC Analysis)

Mn and Mw were measured by GPC in accordance with JP-A-2001-208736 underthe following conditions, and Mw/Mn was determined.

Mobile phase: solvent mixture of R-225 (ASAHIKLIN AK-225SEC Grade 1,manufactured by Asahi Glass Company, Limited) and HFIP (R-255/HFIP=99/1in volume ratio)

Analytical column: serially connected two PLgel MIXED-E columns(manufactured by Polymer Laboratories)

Molecular weight standard samples: four perfluoropolyethers having Mw/Mnless than 1.1 and molecular weights of from 2,000 to 10,000 and oneperfluoropolyether having Mw/Mn of at least 1.1 and a molecular weightof 1,300

Mobile phase flow rate: 1.0 mL/min

Column temperature: 37° C.

Detector: evaporative light scattering detector

(Contact Angle)

Contact angles on lubricant coatings were measured with a contact anglemeter (CA-X, manufactured by Face). The contact angles between fivedrops of water or hexadecane with a volume of about 2 μL and the surfaceof each lubricant coating were measured and averaged.

(Friction Coefficient)

The friction coefficient on the surface of each lubricant coating wasmeasured with a friction meter (Tribogear, manufactured by Heidon) usinga SUS ball with a diameter of 10 mm as a contactor under a load 2 kgload at 25 rpm.

(Transfer Test)

After the measurement of friction coefficient, the surface of thecontactor was inspected under an optical microscope for lubricanttransfer at the four contact points and rated as ◯ when no lubricanttransfer was observed, as Δ when lubricant transfer was observed at 1 to3 contact points and as x when lubricant transfer was observed at allthe four contact points.

(Metal Ion Analysis)

The metal ion content in 1.0 g of each fraction was determined byashing-inductively coupled plasma-mass spectroscopy.

(Anion Analysis)

1.0 g of each fraction or 30 g of ultrapure water was stirred in apolytetrafluoroethylene bottle preliminarily washed with dilute aqueoussodium hydroxide for 24 hours to prepare a sample, and the anion contentwas determined by water extraction-ion chromatography.

(Water Content)

The water content in each fraction was measured by Karl-Fischercoulometric titration.

Example 1

Polyoxyethylene glycerol ether (Uniox G1200, manufactured by NOFCORPORATION) was reacted with FCOCF(CF₃)OCF₂CF(CF₃)O(CF₂)₃F in the samemanner as in Example 11 of Patent Document 1 to obtain a compound (B-1),which was liquid at room temperature. NMR analysis revealed that in thecompound (B-1), the average of (k+r+p) was 20.5, R^(f) was—CF(CF₃)OCF₂CF(CF₃)OCF₂CF₂CF₃, the Mn was 2,600, and the Mw/Mn was 1.15.

¹H-NMR (solvent: CDCl₃) δ(ppm): 3.4 to 3.8, 4.5.

¹⁹F-NMR (solvent: CDCl₃) δ(ppm): −76.0 to −81.0, −81.0 to −82.0, −82.0to −82.5, −82.5 to −85.0, −128.0 to −129.2, −131.1, −144.7.

Example 2

Liquid phase fluorination was carried out in the same manner as inExample 2-1 in Patent Document 1 except that R-113 was replaced withCFE-419, and the compound (D3-1) was replaced with the compound (B-1) toobtain a composition (c-1). The composition (c-1) contained a compound(C-1) as a main component, and in the composition, at least 99.9 mol %of the hydrogen atoms in the compound (B-1) had been replaced byfluorine atoms.

Example 3

Liquid phase fluorination was carried out in the same manner as inExample 2 except that the fluorine gas concentration in the gals blowninto the liquid phase was changed from 20 vol % to 10 vol % to obtain acomposition (c-2).

Example 4

Liquid phase fluorination was carried out in the same manner as inExample 2 except that the fluorine gas concentration in the gals blowninto the liquid phase was changed from 20 vol % to 50 vol % to obtain acomposition (c-3).

¹H-NMR (solvent: CDCl₃) δ(ppm): 5.9 to 6.4.

¹⁹F-NMR (solvent: CDCl₃) δ(ppm): −55.8, −77.5 to −86.0, −88.2 to −92.0,−120.0 to −139.0, −142.0 to −146.0.

Example 5

Example 3 in Patent Document 1 was followed except that the compound(D4-1) was replaced with the composition (c-1), with the composition(c-2) and with the composition (c-3), to obtain a composition (d-1), acomposition (d-2) and a composition (d-3) each containing a compound(D-1) as a main component.

Example 6

Example 4-1 in Patent Document 1 was followed except that the compound(D5-1) was replaced with the composition (d-1), with the composition(d-2) and with the composition (d-3), to obtain a composition (e-1), acomposition (e-2) and a composition (e-3) each containing a compound(E-1) as a main component.

Example 7

Example 5 in Patent Document 1 was followed except that the compound(D7-1) was replaced with the composition (e-1), with the composition(e-2) and with the composition (e-3), to obtain a composition (a-1), acomposition (a-2) and a composition (a-3) each containing a compound(A11-1) as a main component.

NMR analysis and HPLC analysis revealed that each of the resultingcompositions contained compounds having two terminal OH groups (A21-1a)and (A21-1b) (hereinafter the compounds (A21-1a) and (A21-1b) arecollectively referred to as (A21-1)) and compounds having one terminalOH group (A31-1a) and (A31-1b) (hereinafter the compounds (A31-1a) and(A31-1b) are collectively referred to as (A31-1)).

The NMR spectrum patterns of the compound (a-1), the composition (a-2)and the composition (a-3):

¹H-NMR δ(ppm): 3.94.

¹⁹F-NMR δ(ppm): −54.0, −80.1, −88.2 to −90.5, −135.0 to −139.0.

The results of NMR analysis, HPLC analysis and GPC analysis are shown inTable 1.

The ratio of terminal OH groups to terminal CF₃ groups in the moleculewere calculated from the ratio of the area of the peak attributed to thefluorine atoms in CF₃ groups around −54.0 ppm to the area of the peakattributed to the fluorine atoms in CF₂ groups in CF₂CH₂OH groups around−80.1 ppm.

TABLE 1 NMR analysis Fluorine gas Ratio of terminal HPLC analysis GPCconcentration functional groups [%] Compositional ratio [%] analysisComposition [%] CF₃OCF₂— —CF₂CH₂OH A31-1 A21-1 A11-1 Mn Mw/Mn a-1 20 793 1 18 81 2,000 1.07 a-2 10 3 97 1 9 90 2,100 1.05 a-3 50 21 79 20 3050 1,850 1.13

Example 8

The composition (a-3) was purified by column chromatography as follows.

A slurry of a particulate silica gel (MS-Gel D75-120A, manufactured byS. I. Tech Co., Ltd.) in R-225 was packed into a column with a diameterof 150 mm and a length of 500 mm to form a silica gel bed with a heightof 100 mm.

150 g of the composition (a-3) was loaded on the silica gel bed andfractionated by using extraction solvents (solvent mixtures of R225 andIPA) with gradually increasing IPA concentrations to obtain fractions(p1-1) to (p1-5). The volumes of the extraction solvents, the IPAconcentrations in the extraction solvents and the masses of thefractions are shown in Table 2.

TABLE 2 IPA concentration Volume of extraction solvent Fraction [%] [L]Mass [g] p1-1 0 5 50 p1-2 20 3 35 p1-3 50 3 32 p1-4 70 3 15 p1-5 100 5 3Total: 135 Loaded amount: 150

Each fraction was analyzed by HPLC and GPC. The results are shown inTable 3.

TABLE 3 HPLC analysis GPC compositional ratio [%] analysis A31-1 A21-1A11-1 Mn Mw/Mn a-3 20 30 50 1,850 1.15 p1-1 37 48 15 1,750 1.15 p1-2 2039 41 1,810 1.13 p1-3 1 23 76 1,850 1.14 p1-4 0 10 90 1,860 1.10 p1-5 06 94 2,100 1.10

In the extraction by column chromatography, because of the influence ofthe number of terminal hydroxyl groups, the proportions of the compound(A21-1) and the compound (A31-1) were high in less polar fractions, andthe proportion of the compound (A11-1) was high in more polar fractions.

Example 9

The fraction (p1-3) was purified by supercritical extraction as follows.

A thick-walled stainless steel vessel (inner diameter φ33 mm×depth 45mm) having an inlet and an outlet, a supercritical carbon dioxidedelivery pump (SCF-210, manufactured by JASCO Corporation), an automaticback pressure regulator (880-01, manufactured by JASCO Corporation) andan ordinary chromatographic column oven were assembled into anapparatus.

30 g of the fraction (p1-3) was injected into the vessel, andsupercritical carbon dioxide was feed at a flow rate of 2.5 cc/min interms of liquid carbon dioxide. The pressure in the vessel was changedwith time, while the temperature in the vessel was maintained at 60° C.,and extracts at different pressures were collected as fractions (p2-1)to (p2-7). The pressure in the vessel, the pressure holding time and theamounts of the fractions are shown in Table 4.

TABLE 4 Fraction Pressure [MPa] Holding time [min] Mass [g] p2-1 10 → 1175 → 120 0.25 p2-2 12 120 1.81 p2-3 13 120 5.46 p2-4 13.5 120 8.26 p2-514 120 9.17 p2-6 15 120 3.63 p2-7 16 → 20 → 25 90 → 60 → 60 0.60 Residue0.01 Extracts + residue: 29.19 Injected amount: 30

Each fraction was analyzed by HPLC, NMR and GPC. The results are shownin Table 5. In the supercritical extraction, because of the influence ofmolecular weight, molecules were extracted in the ascending order ofmolecular weight.

TABLE 5 HPLC analysis GPC compositional ratio [%] analysis A31-1 A21-1A11-1 Mn Mw/Mn p1-3 1 23 76 1,850 1.15 p2-1 37 53 9 1,750 1.1 p2-2 20 5327 1,980 1.08 p2-3 6 42 51 2,030 1.09 p2-4 1.3 30 68 2,150 1.10 p2-5 0 496 2,500 1.14 p2-6 0 2 98 2,700 1.79 p2-7 0 0 100 — —

Each fraction was examined on the solubility in R-225, Vertrel XF(manufactured by Du Pont) and AE-3000 (manufactured by Asahi GlassCompany, Limited). Each fraction was mixed with the solvents at aconcentration of 1 mass %, and the solubilities were examined visually.All the fractions were soluble in all the solvents.

Examples 10 to 12 Working Examples

A carbon protective layer was formed on glass blanks for magnetic disks(2.5″ blanks, manufactured by Asahi Glass Company, Limited) bydepositing DLC (diamond-like carbon) by radio-frequency magnetronsputtering using a carbon target to obtain stimulant disks. The Ar gaspressure was 0.003 Torr, and the input power density on the target was 3W/cm². The carbon protective layers were 30 nm thick. The water contactangle on the carbon protective layers was 40°.

The fractions (p2-2), (p2-3) and (p2-5) were diluted with Vertrel XF toobtain solvent compositions having a fraction concentration of 0.01 mass%.

The stimulant disks were dipped in the solvent compositions for 30seconds and pulled out at a constant rate of 6 mm/sec. The stimulantdisks coated with the solvent compositions were subjected to heattreatment in a thermostatic oven at 100° C. for 1 hour to form lubricantcoatings. The disks having lubricant coatings were rinsed with VertrelXF for 30 seconds by dipping. The thicknesses of the lubricant coatingswere measured with an ellipsometer before and after rinsing to determinethe bonding ratios. The contact angles and friction coefficients on thesurfaces of the lubricant coatings were measured. After measurement offriction coefficients, the surface of the contactor was inspected underan optical microscope for lubricant transfer. The results are shown inTable 6.

Example 13 Reference Example

A lubricant coating was formed on the surface of a stimulant disk in thesame manner as in Example 1 except that the fraction (p2-2) was replacedwith the compound (F) (FOMBLIN Z-TetraOL, Mn: 3,000, Mw/Mn=1.23,manufactured by Solvay) and evaluated in the same manner as in Example10. The CF₃ ratio in the compound is 0.

HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂O)_(i)(CF₂CF₂O)_(ii)—CF₂CH₂OCH₂CH(OH)CH₂OH  (F)

wherein i/ii=1.0.

Examples 14 and 15

Lubricant coatings were formed on stimulant disks in the same manner asin Example 10 except that the fraction (p2-2) was replaced with thefraction (p2-6) or (p2-7) and evaluated in the same manner as in Example10. The results are shown in Table 6.

TABLE 6 Coating Bonding Friction CF₃ Contact angle [°] thickness ratiocoefficient Transfer Ex. ratio Water Hexadecane [mm] [%] [—] test 10p2-2 0.31 108 76 1.5 60 1.2 ◯ 11 p2-3 0.18 102 72 1.8 75 1.2 ◯ 12 p2-50.013 88 61 2.1 82 1.4 ◯ 13 FOMBLIN Z 0 93 62 1.6 80 3.2 ◯ TetraOL 14p2-6 0.007 n.d. n.d. n.d. n.d. n.d. ◯ 15 p2-7 0 n.d. n.d. n.d. n.d. n.d.X

The results of Examples 10 to 12 indicate that a composition comprisingPFPEs having three terminal groups having specific structures at themolecular terminals can provide a surface with a high bonding ratio, alarge contact angle and a small friction coefficient, when the OH/CH₃ratio is more than 2 and at most 100.

Example 16

Metal ion and anion analyses of the fractions (p2-2), (p2-3) and (p2-5)and measurement of their water contents were carried out. The resultsare shown in Table 7.

TABLE 7 p2-2 p2-3 p2-5 Metal ions Al 10 <1 30 [ppb] Na 260 130 200 K 6011 35 Mg 70 300 400 Ca 350 800 200 Cr 3 n.d. 1 Mn n.d. n.d. 3 Fe 10 8 20Co n.d. n.d. n.d. Ni 5 3 10 Cu 3 n.d. 3 Zn 10 8 10 Ba 2 n.d. 3 Pb n.d.n.d. n.d. Anions F 650 1,600 1,800 [ppb] Formic acid n.d. n.d. n.d. Cl620 230 110 NO₃ n.d. 120 230 SO₄ 930 360 550 Oxalic acid 900 700 1,100Water 960 940 900 content [ppm] n.d. not detected

INDUSTRIAL APPLICABILITY

The ether composition of the present invention shows a high bondingratio, forms a coating having a low friction coefficient surface and isuseful as a lubricant to be applied on the surface of magnetic recordingmedia.

The entire disclosures of Japanese Patent Application No. 2007-327619filed on Dec. 19, 2007 and Japanese Patent Application No. 2008-196370filed on Jul. 30, 2008 including specifications, claims and summariesare incorporated herein by reference in their entireties.

1. An ether composition comprising at least two compounds selected fromthe group consisting of a compound represented by the following formula(A1), a compound represented by the following formula (A2) and acompound represented by the following formula (A3), wherein the totalnumber of moles of CF₃ groups in the group represented by the followingformula (Z) in relation to the sum of the total number of moles of CF₃groups in the group represented by the following formula (Z) and thetotal number of moles of OH groups in the group represented by thefollowing formula (X) (CF₃/(OH+CF₃)) is at least 0.001 and at most 0.30:(X—)₃Y³  (A1),(X—)₂Y³—Z  (A2),X—Y³(—Z)₂  (A3). Wherein X is a group represented by the followingformula (X), Y³ is a perfluoroalkane-triyl group or aperfluoroalkane-triyl group having an etheric oxygen atom insertedbetween carbon-carbon atoms, provided that when Y³ has a CF₃ group, theCF₃ group is bonded to a quaternary carbon,HO—(CH₂CH₂O)_(a).(CH₂CH(OH)CH₂O)_(b)-Q-  (X),CF₃(CF₂)_(s)O(CF₂CF₂O)_(g)—  (Z). Wherein in the above formulae (X) and(Z), a is an integer of from 0 to 100, b is 0 or 1, s is an integer offrom 0 to 19, g is an integer of from 3 to 200, and Q is apolyfluorinated polymethylene group, a polyfluorinated polymethylenegroup having an etheric oxygen atom bonded between carbon-carbon atoms,a polyfluorinated polymethylene group having an etheric oxygen atombonded to the terminal carbon atom bonded to Y³ or a polyfluorinatedpolymethylene group having an etheric oxygen atom bonded betweencarbon-carbon atoms and an etheric oxygen atom bonded to the terminalcarbon atom bonded to Y³.
 2. The ether composition according to claim 1,wherein X is a group selected from the group consisting of a grouprepresented by the following formula (X1), a group represented by thefollowing formula (X2), a group represented by the following formula(X3) and a group represented by the following formula (X4):HOCH₂CF₂O(CF₂CF₂O)_(d)—  (X1),HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂CF₂O)_(d)—  (X2),HOCH₂CH₂CF₂O(CF₂CF₂O)_(d)—  (X3),HOCH₂CH₂OCH₂CF₂O(CF₂CF₂O)_(d)—  (X4), wherein d is an integer of from 1to
 200. 3. The ether composition according to claim 1, wherein Y³ is agroup selected from the group consisting of a group represented by thefollowing formula (Y³-1), a group represented by the following formula(Y³-2) and a group represented by the following formula (Y³-3).


4. The ether composition according to claim 1, wherein the compoundrepresented by the formula (A1) is a compound represented by thefollowing formula (A1-1), the compound represented by the formula (A2)is a compound represented by the following formula (A2-1a), a compoundrepresented by the following formula (A2-1b) or a combination of acompound represented by the following formula (A2-1a) and a compoundrepresented by the following formula (A2-1b), and the compoundrepresented by the formula (A3) is a compound represented by thefollowing formula (A3-1a), a compound represented by the followingformula (A3-1b) or a combination of a compound represented by thefollowing formula (A3-1a) and a compound represented by the followingformula (A3-1b).


5. The ether composition according to claim 1, wherein the compoundrepresented by the formula (A1), the compound represented by the formula(A2) and the compound represented by the formula (A3) have no —OCF₂O—structure.
 6. The ether composition according to claim 1, wherein thetotal amount of the compound represented by the formula (A1), thecompound represented by the formula (A2) and the compound represented bythe formula (A3) is at least 95 mass % in relation to the ethercomposition.
 7. The ether composition according to claim 1, which has anumber average molecular weight of from 500 to 1,000,000 and a molecularweight distribution (mass average molecular weight/number averagemolecular weight) of from 1.01 to 1.5.
 8. A lubricant containing theether composition as defined in claim 1.